This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-321596, filed Oct. 20, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a light-emission display panel for displaying an image by using a plurality of self light-emission elements and to a method of manufacturing the light-emission display panel.
2. Description of the Related Art
In recent years, a light-emission display panel such as an organic EL (Electro Luminescence) display device has attracted attention as a monitor display for a notebook type personal computer, a mobile information terminal or the like because the light-emission display panel is lightweight, thin and high in brightness. A typical organic EL display device is configured to display an image with a matrix array of organic EL elements used as pixels. In the organic EL display device, a plurality of scanning lines are arranged along the rows of these organic EL elements, and a plurality of signal lines are arranged along the columns of these organic EL elements. Further, a plurality of pixel switches are arranged near the intersections of the scanning lines and the signal lines. Each of the pixel switches applies a signal voltage from a corresponding signal line to a corresponding organic EL element when the pixel switch is driven through a corresponding scanning line.
FIG. 5 shows the pixel portion structure of the organic EL display device. As shown in the drawing, the organic EL element comprises a structure in which a light-emitting layer 1 is formed of a thin film containing an electro-luminescence-organic-compound of red, green or blue, and interposed between a cathode 2 and an anode 3. Electrons and holes are supplied into the light-emitting layer 1 and recombined so as to produce excitons. The light is emitted from the light-emitting layer when the excitons are deactivated. It should be noted that a buffer layer 4 is arranged between the light-emitting layer 1 and the anode 3 so as to produce the excitons efficiently. The anode 3 is a transparent electrode formed of, for example, ITO (Indium Tin Oxide), and the cathode 2 is a reflection electrode formed of a metal such as aluminum. Because of the particular construction, the organic EL element is capable of producing a brightness of about 100 to 100,000 cd/m2 by the application of a voltage not higher than 10V.
The pixel switch is formed of, for example, a thin film transistor. The thin film transistor comprises a semiconductor thin film 6 formed on a glass substrate 5, a gate insulating film 7 covering the semiconductor thin film 6, a gate electrode 8 formed on the semiconductor thin film 6 with the gate insulating film 7 interposed therebetween, and source and drain electrodes 10 and 11 connected to the source and drain regions, respectively, formed on both sides of the gate electrode 8. The semiconductor thin film 6 is formed of, for example, amorphous silicon or polysilicon. The gate electrode 8 and the semiconductor thin film 6 are covered with an interlayer insulating film 9 formed with contact holes exposing the source and drain regions. The source electrode 10 and the drain electrode 11 are formed on the interlayer insulating film 9 in contact with the source and drain regions of the semiconductor thin film via the contact holes. Also, the source electrode 10 and the drain electrode 11 are covered with an interlayer insulating film 12 formed with a contact hole exposing the source electrode 10.
It should be noted that the thin film of the electro-luminescence-organic-compound tends to absorb moisture, and thereby becomes unusable. Thus, this thin film does not have a resistance to a photolithographic patterning process, for example. In the process of forming the organic EL element, the anode 3 is formed on the interlayer insulating film 12 in contact with the source electrode 10 via the contact hole of the interlayer insulating film 12. The anode 3 and the interlayer insulating film 12 are covered entirely with a protective film 13, and the protective layer 13 is covered entirely with an insulating film 14. The protective film 13 and the insulating film 14 are patterned to form an opening which exposes part of the anode 3. The buffer layer 4 is formed of a buffer material coated to cover the exposed portion of the anode 3 in the opening. The light-emitting layer 1 is formed of an electro-luminescence-organic-compound coated on the buffer layer 4. Further, the cathode 2 is formed on the light-emitting layer 1 by means of vapor deposition of a metal.
In a case where the organic EL element is formed through the steps described above, it is, however, necessary for the light emitted from the light-emitting layer 1 to pass through the interlayer insulating film 9 and the interlayer insulating film 12 for illuminating the outer space of the glass plate 5. As a result, the light transmittance is lowered.
An object of the present invention is to provide a light-emission display panel with an excellent light-emitting property without requiring a complicated manufacturing process.
According to a first aspect of the present invention, there is provided a light-emission display panel, which comprises self light-emission elements in which a self light-emitting layer is held between first and second electrodes, and pixel wiring members for pixels formed of the self light-emission elements, wherein the first electrode having a light transmitting property, and each pixel wiring member includes metal wirings which are formed together with the first electrode in the same plane over a light transmitting dielectric plate to reflect the light emitted laterally from the self light-emitting layer.
According to a second aspect of the present invention, there is provided a light-emission display panel, which comprises self light-emission elements in which a self light-emitting layer is held between a transparent electrode and a reflection electrode, pixel wiring members for pixels formed of the self light-emission elements, and an insulating member which includes an interlayer insulating film covering the pixel wiring member and the transparent electrode and a water repellent insulating film covering the interlayer insulating film, wherein the self light-emitting layer is formed within an opening of the insulating member which is tapered toward and exposes part of the transparent electrode.
According to a third aspect of the present invention, there is provided a method of manufacturing a light-emission display panel having a matrix array of self light-emission elements in which a self light-emitting layer is held between a transparent electrode and a reflection electrode and a light is externally radiated through the transparent electrode, the method comprising formation of a semiconductor layer in an island form on a transparent dielectric plate, formation of a gate electrode on the semiconductor layer via a gate insulating film, formation of an interlayer insulating film on the gate insulating film and the gate electrode, formation of the transparent electrode on a selected area of the interlayer insulating film, and formation of a metal electrode which contacts the semiconductor layer via an opening formed in the interlayer insulating film and the gate insulating film after formation of the transparent electrode.
With the light-emission display panel according to the first aspect of the present invention, the metal wiring is formed together with the first electrode in the same plane over a light transmitting dielectric plate to reflect the light emitted laterally from the self light-emitting layer. This permits an increase in the intensity of the light radiated to the outside of the light transmitting dielectric plate. Further, since the metal wiring and the first electrode are formed in the same plane, it is unnecessary to form two light transmitting dielectric layers by independent processes. In addition, the light transmittance is prevented from being lowered due to an overlap of the two light transmitting dielectric layers.
With the light-emission display panel according to the second aspect of the present invention, the insulating film is covered with the water repellent insulating film to impart water-repellent properties to the inner wall of the opening on a side apart from the exposed surface of the transparent electrode. It follows that, where a predetermined amount of an electro-luminescence-organic-compound, which is used as the material of the self light-emitting layer, is jetted into the opening by an ink jet process, the electro-luminescence-organic-compound is not attached to the water repellent part of the inner wall of the opening and, thus, flows down promptly. As a result, the self light-emitting layer of a uniform and sufficient thickness can be formed on the transparent electrode exposed by the opening.
In the method of manufacturing a light-emission display panel according to the third aspect of the present invention, the opening receiving the metal electrode, which contacts the semiconductor layer, is formed after formation of the transparent electrode and the metal electrode is formed in this order. Therefore, it can be prevented that the semiconductor layer surface suffers damage during formation of the transparent electrode. Moreover, it can be prevented that the metal electrode is undesirably processed by etchant used during formation of the transparent electrode.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.